1. Technical Field
The present invention relates to printing apparatuses.
2. Related Art
User-replaceable ink cartridges (an example of an ink holding unit) used in ink jet printers, which are an example of a printing apparatus, are sometimes provided with storage devices for managing a consumed ink amount, or in other words, an amount of ink consumed from the ink cartridge. In printing apparatuses where an ink tank (an example of an ink holding unit) provided in the printing apparatus is filled with ink, too, a memory unit including a storage device is sometimes installed in the printing apparatus in order to manage the consumed ink amount. Information such as the color of the ink, the consumed ink amount, and so on is stored in this storage device.
JP-A-2014-46545 discloses a technique in which each time a total consumed ink amount on a printing apparatus main unit (called simply a “main unit” hereinafter) side exceeds a first threshold (WTH1), information of the main unit-side total consumed ink amount managed on the main unit side is written into a memory unit. JP-A-2014-46545 also discloses a technique where the stated write is carried out before the main unit-side total consumed ink amount exceeds a second threshold (WTH2), and in the case where WTH2 has been exceeded, the memory unit is set to an invalid state and no additional writes are carried out.
Meanwhile, JP-A-2008-254395 discloses a technique in which an identification number and a capacity of a set memory card are stored in a storage unit of a printing apparatus. In JP-A-2008-254395, the storage unit of the printing apparatus stocks liquid stock amount information so that a liquid stock amount is added on the basis of the information in the set memory card, regardless of whether it is before or after ink has been refilled. JP-A-2011-73208 also discloses a technique in which an ink amount in a separate memory is added to an amount of ink that can be used by a printer.
According to the technique of JP-A-2014-46545, a process for writing into the memory unit is carried out until the main unit-side total consumed ink amount exceeds WTH2, and thus printing operations will stop if a user removed the memory unit before the main unit-side total consumed ink amount exceeds WTH2. Thus in order to print continuously, the user is forced to replace the memory unit during a specific period, namely after the main unit-side total consumed ink amount has exceeded WTH2 but before printing operations end in response to a determination that the ink has run out (that is, a case where the main unit-side total consumed ink amount has exceeded a third threshold WTH3). This places a heavy burden on the user. The printing operations will stop unless this replacement is made, and there is thus a problem that it is difficult to use the printing apparatus continuously for long periods of time.
According to the techniques disclosed in JP-A-2008-254395 and JP-A-2011-73208, information in a plurality of memory cards or in a separate memory card can be added to the liquid stock amount on the main unit side, and printing can be carried out continuously until the amount of ink corresponding to the ink amount stored on the main unit side runs out. However, in the case where an error occurs in the printing apparatus main unit and the ink amount information is lost, the information loss may render the stocked (charged) ink unusable, which is an undesirable situation.
Thus what is needed is a printing apparatus that can properly manage ink even during breakdowns while making it possible to print continuously with little burden on a user.